I'm not even a JavaScript hater, but: its relation to C is merely syntactic, and is to its detriment, frankly. And, simple? Assuming a hypothetical comprehensive encoding of programming language semantics, I can't imagine that JS would be anywhere near the top of the list for shortest complete descriptions of same. That and the constant churn of libraries du jour in the JS world makes me think that it is far from an optimal language for the beginning programmer.
Javascript is probably semantically closest to Scheme - it's a language built around closures and one universal data type (lists in Scheme, objects/dicts in JS). Scheme is a pretty good choice for intro CS courses, because of its simplicity and the need to re-implement many common language constructs from first principles.
JS shares this property, but also gains the benefits of being widely used in industry and available in every web browser, with a good debugger in Firefox and Chrome. I'd never really considered it as a teaching language, but I think it'd be a great choice.
Immutability-by-default is a necessary, if not sufficient component of the semantics of Scheme that is lacking in JavaScript, and it's that same lack that leads me to think that any comparison between the two languages is basically spurious.
Scheme certainly has mutability, through set!, set-car!, set-cdr!, and procedures based upon them. It's not the default - you always know when you're mutating something - but then, there's a pretty direct syntactic translation into Javascript, where = without a var always means you're mutating something.
Why is this important for students, anyway? Shouldn't they be exposed to mutability fairly early on?
It's not important for students, I just dispute the notion that JavaScript has any special affinity with Scheme beyond that of any other language with first-class functions. Anyway, the major advantage of immutability by default is that it enables under-the-hood optimizations like structural sharing that make FP the paradigm of least resistance. To the extent that JavaScript doesn't do that, it doesn't really deserve to be called a functional language any more than e.g. Ruby.
JS certainly does have other influences, notably Self and Java. But from that article:
"As I’ve often said, and as others at Netscape can confirm, I was recruited to Netscape with the promise of “doing Scheme” in the browser....I’m not proud, but I’m happy that I chose Scheme-ish first-class functions and Self-ish (albeit singular) prototypes as the main ingredients. The Java influences, especially y2k Date bugs but also the primitive vs. object distinction (e.g., string vs. String), were unfortunate."
Did you have tons of C/C++ libraries thrown at you in 100 level courses? Probably not, I'm guessing.
JavaScript is great because it runs in a browser, provides immediate feedback without having to compile/recompile and allows for all the simple flow control concepts mentioned by other posters.
I don't see running in the browser as a benefit. It means that a required step for a neophyte in producing meaningful output is getting a handle on the utterly brain-dead DOM API.
But then the mere fact that a computer comes with a browser already installed is not a notable advantage. I can get a Python REPL running on a computer with an amount of effort and know-how comparable to that necessary to install Chrome.
